director cosines

[malmeida2019]

Good morning friends of the group, sorry if my questions are easy, but I'm new to Mathcad. I don't know how to solve this type of equation, I would like the answer to be in degrees.The answer must be 120º.

[Cornel · Accepted solution]

So, the answer seems to be 45 deg (at least with your above given equation for calculating ), not 120 deg...

Are you sure that the answer must be 120 deg?

So, the correct formula for y2 is:

where:

[malmeida2019]

TKS

[malmeida2019]

[Cornel]

Your calculation formula for y2 in your Mathcad file was wrongly derived...see my above post

[Werner_E]

Some additional remarks:

The symbolics does not know anything about units, it does not know deg or °. This is the reason why the symbolic result shown on Cornels answer still includes the expressions cos(60°), etc.

If you like you can redefine the used units at the top of the sheet (maybe in a collapsed region)

Now the symbolic result looks less ugly (and of course its in radian, not degree)

Your equation has an infinite number of solutions and if you know in which range you are looking for the solution (maybe between 90° and 180 °) you can tell Primes symbolics (using the "assume" modifier) to give you just the needed solution

If you have (re)defined the unit ° as explained above, you can also use degree in the assume modifier (the result will always be shown in radiant)

[malmeida2019]

thank my friend for the brilliant explanation. Thank you